She is the leader of the Sisterhood, a secretive and powerful matriarchal order whose members undergo intense physical training and mental conditioning to obtain superhuman abilities.

Set in Frank Herbert's Dune universe, ten thousand years before the events of his 1965 novel Dune, the series follows Valya and her sister, Tula Harkonnen (Olivia Williams), as they combat forces that threaten humanity's future, and shape the Sisterhood's evolution into the Bene Gesserit order.

Valya first appears in the Great Schools of Dune (2012–2016) prequel trilogy of novels by Brian Herbert and Kevin J. Anderson.

[8] This secretive, matriarchal order also continues to acquire power and influence as a means to direct the Imperium, and thereby humanity, on the path they have set for it.

And nothing, nothing in this world is good and bad; everything is compromised and strange, and yet what Valya Harkonnen sets her sights on is really determining the right path for humankind.

"[12] In the series, Mother Superior Valya schemes on a long term scale that involves fellow Sisters, Imperial power players and Emperor Javicco Corrino (Mark Strong) himself.

[12] In the series premiere "The Hidden Hand", young Valya Harkonnen has joined the Sisterhood on Wallach IX to escape her family's exile to a desolate world.

Desmond explains to Pruwet that the Sisterhood has unacceptable influence over the Imperium, and confesses that he has been given a "great power" by his near-death experience on Arrakis.

Her parents, Sonia and Vergyl, and uncle, Evgeny, are content living a quiet life on the ice planet Lankiveil.

Valya's brother, Griffin, shares her desire to restore their family's reputation, but is subsequently killed, allegedly murdered by Vorian.

Valya leaves to join the Sisterhood, the elder Harkonnens blaming her for Griffin's death, but resists taking her vows because she still considers her family's vengeance her top priority.

Raquella takes Valya under her wing, eventually sharing with her the secret of the forbidden technology used to maintain her vast DNA database.

In The Battle of Corrin, Abulurd Harkonnen defies an order from his commander, Vorian Atreides, that would sacrifice many lives, and in doing so causes even more deaths.

"[21] Valya singlehandedly ignites the Harkonnen-Atreides feud and mobilizes her siblings to the cause, while taking control of the fledgling Bene Gesserit and shaping it to her will as a formidable force in the universe.

[20][21] In Sisterhood of Dune, the remnants of House Harkonnen live a simple existence as whalers on the ice planet Lankiveil.

Valya's rival in the Sisterhood, Sister Dorotea, is a Butlerian sympathizer who discovers the existence of Raquella's computers and reports it to Salvador.

Valya helps Raquella remove them in advance of the Emperor's invasion, but a petulant Salvador disbands the Sisterhood School on Rossak.

She swallows and survives the dangerous Rossak drug and gains access to the memories and mental presences of her female ancestors, becoming the third Reverend Mother after Raquella and Dorotea.

Nearing the end of her life, Raquella believes that the only hope for the Sisterhood to survive is for the Wallach IX sisters to reconcile with Dorotea's faction.

Vorian, feeling guilty for Griffin's death, tries to help the struggling Harkonnens with a secret infusion of funds to their whaling business on Lankiveil.

He visits the planet Caladan to meet his descendants there, just in time for young Orry Atreides to be slain on his wedding night by his new bride: Griffin and Valya's younger sister, Tula.

Tula, who had come to love Orry and fled out of guilt for murdering him, is hunted and nearly killed by his brother Willem Atreides and Vorian.

Valya finds that Vorian is immune to the Voice, and Willem stops short of killing Tula when she reveals she is carrying Orry's child.

Valya guides her young brother Danvis Harkonnen as he begins service in the royal court, and resumes her duties as leader of the Bene Gesserit.